It is important for designers and manufacturers to have accurate knowledge of the surface temperature of a monolithic integrated circuit (hereinafter referred to as IC). The presence of "hot spots" on the surface of an IC may create reliability and performance problems. If the location of such hot spots are known with high resolution, designers may be able to modify the IC layout to optimize dissipation or mitigate the problem via other techniques known to those in the art.
Prior art methods of mapping the surface temperature of an IC include infrared thermography and the use of an array of temperature sensitive elements such as thermocouples, thermistors, RTD's, and bipolar junction sensors. Such prior art methods typically suffer from poor spatial resolution.
Prior art methods have used nematic liquid crystals (hereinafter referred to as NLCs) as a means for locating hot-spots on ICs and mapping the surface temperature of an IC. However, these previous computerized analytical methods have had limited success due primarily to their inability to reliably discriminate between actual hot-spots on the IC, the background features of the IC substrate and the potentially spurious behavior and visible internal artifacts associated with NLC materials. These prior art NLC methods have also experienced poor spatial resolution, and non-repeatable results.
Since modem IC's are typically fabricated on a sub-micron scale, low resolution temperature mapping makes it difficult to resolve and isolate the occurrence of nearly-adjacent IC hot spots using prior art techniques.
It is an object of this invention to provide a temperature mapping system and method which significantly overcomes the aforementioned problems inherent in the prior art.
It is another object of this invention to provide a temperature mapping system which provides spatial resolution sufficient to detect and resolve nearly-adjacent hot spots on the surface of an IC.